1. Field of the Invention
The present invention relates to a method of testing a split ceramic alignment sleeve used in an optical fiber connector used in optical fiber communications and an apparatus therefor.
2. Description of Prior Art
A typical conventional optical fiber connector has a well-known structure in which an optical fiber is fixed at the center of a solid cylindrical ferrule, the resultant assembly is fitted in a hollow cylindrical alignment sleeve having an accurate inner diameter, and end faces of the ferrules are aligned with and abut against each other.
The most popular alignment sleeve used in the above optical fiber connector is a split alignment sleeve having a slit in an axial direction of the solid cylindrical ferrule. A typical example of the conventional split alignment sleeve is made of phosphor bronze. However, split ceramic alignment sleeves are also manufactured. In particular, a split zirconia ceramic alignment sleeve having the same material as a zirconia ferrule is used in a connection of the zirconia ceramic ferrules having mating portions made of zirconia ceramics. It is known that more stable connection characteristics than those obtained by using the split phosphor bronze alignment sleeve can be obtained (JAP-PAT-KOKAI NO. 33110/1990).
The following conventional method is known for evaluating a defective/nondefective split ceramic alignment sleeve before it is used in an optical fiber connector.
First of all, flaw detection of a split alignment sleeve is generally performed as quality control in the manufacture. More specifically, a flaw on the surface of a split alignment sleeve is dyed with a dyestuff, and the presence/absence of a flaw is visually checked. This method is called a color check method. Alternatively, light from a light source is transmitted through a split alignment sleeve to check the presence/absence of the flaw. In these test methods, a quantitative test of split ceramic alignment sleeves cannot be performed.
A load test method capable of applying a specific mechanical load on each split alignment sleeve to perform a quantitative test for the life of split ceramic alignment sleeves, which test has been rarely satisfactorily performed by the conventional flaw detection methods, is disclosed (JAP-PAT-KOKAI NO. 231545/1990).
FIG. 1 shows a test method in which L-shaped upper and lower loading parts A and B are inserted into a slit 3 of a split ceramic alignment sleeve 2 and test loads are applied to the L-shaped upper and lower loading parts A and B to open the slit 3. FIG. 2 shows another test method in which test loads are applied to flat upper and lower loading parts C and D so as to clamp the split ceramic alignment sleeve 2.
These load test methods can quantitatively perform a test of split ceramic alignment sleeves and can supply highly reliable split ceramic alignment sleeves. Regardless of these advantages, the method relying on a tensile strength test tool, as shown in FIG. 1, requires cumbersome operations for attaching the L-shaped upper and lower loading parts A and B into the slit 3 or detaching them from the slit 3, thus degrading operability. In addition, the size of the slit 3 is small, and excessive loads act on the L-shaped upper and lower loading parts A and B to test a high-strength member such as a split ceramic alignment sleeve, thus causing damage to the loading parts A and B. In the method shown in FIG. 2, tensile stresses act on the peripheral portions of the split alignment sleeve 2. This method is not suitable as a test method of a split alignment sleeve generally used to receive tensile stress on the inner circumferential surface of split alignment sleeve 2.